The spine is a flexible column formed of a plurality of bones called vertebrae. The vertebrae are hollow and stacked one upon the other, forming a strong hollow column for support of the cranium and trunk. The hollow core of the spine houses and protects the nerves of the spinal cord. The different vertebrae are connected to one another by means of articular processes and intervertebral, fibrocartilaginous bodies. Various spinal disorders may cause the spine to become misaligned, curved, and/or twisted or result in fractured and/or compressed vertebrae. It is often necessary to surgically correct these spinal disorders.
The intervertebral fibro-cartilages are also known as intervertebral discs and are made of a fibrous ring filled with pulpy material. The discs function as spinal shock absorbers and also cooperate with synovial joints to facilitate movement and maintain flexibility of the spine. When one or more discs degenerate through accident or disease, nerves passing near the affected area may be compressed and are consequently irritated. The result may be chronic and/or debilitating back pain. Various methods and apparatus have been designed to relieve such back pain, including spinal fusion using an interbody spacer or suitable graft using techniques such as Anterior Lumbar Interbody Fusion (ALIF), Posterior Lumbar Interbody Fusion (PLIF), or Transforaminal Lumbar Interbody Fusion (TLIF) surgical techniques. The implants used in-these techniques, also commonly referred to as interbody spacers, are placed in the inter-discal space between adjacent vertebrae of the spine. Many times an exterior plate is used in conjunction with the interbody spacer to hold the adjacent vertebrae while the fusion occurs.
Ideally, the interbody spacer should stabilize the intervertebral space and allow fusion of the adjacent vertebrae. Moreover, during the time it takes for fusion to occur, the interbody spacer should have sufficient structural integrity to withstand the stress of maintaining the space without substantially degrading or deforming and have sufficient stability to remain securely in place prior to actual bone fusion.
Interbody spacers have been used successfully to fuse adjoining vertebral bodies to restore anatomical positioning and eliminate pain caused by a bulging disc. Spacers fit into the disc space and support the vertebral bodies allowing bone fusion to occur between the joint surfaces. The primary technical advances in this market have been in the methods of minimally invasive interbody delivery. Anterior delivery and more recently medial delivery have reduced morbidity and allowed faster patient rehabilitation.
One major obstacle remaining in perfecting these procedures is reducing the displacement of soft tissue structures and the size of tissue dissections to place the relatively large interbodies necessary to properly support the spinal column during the bone remodeling process. Large interbodies also require extensive site preparation and sizing prior to placement. This site prep can cause increased trauma to surrounding structures as instrumentation is manipulated in the disc space.